1. Field Of The Invention
The present invention relates to liquid-filled transformers having tap changers and more particularly to the structure for mounting such tap changers to the transformer tank.
2. Prior Art
On-load tap changers for small and medium-sized regulating transformers are often designed as so-called selector switches, which means that the duties of the tap selector and the diverter switch are combined into one unit. Such a selector switch is usually located in an oil-filled tank mounted onto the transformer tank and separated therefrom by means of an oil-tight barrier, in which a terminal board having terminals for connection of the transformer taps is arranged
Normally, an on-load tap changer of the above type is located so that the terminal board lies parallel to the transformer winding in a vertical direction. Space must then be accommodated at the upper part of the transformer tank for connecting conductors from the regulating winding to the terminal board of the tap changer, which results in an increase of the height of the transformer tank. Another drawback with this manner of enclosure is that the terminal board of the tap changer is only accessible for connection from above through the opening which is normally covered by the cover of the transformer tank. For the person carrying out the connection work this means an uncomfortable operating position and other disadvantages from the point of view of the work environment. In certain cases, for example, the fitter has to perform the connection in a lying position on top of the upper yoke of the transformer core while the core and the windings are still hot from oil impregnation. Such mounting also results in the tap changer being positioned at such a high level above the ground that it can no longer be mechanically built together with its associated operating device, which has to be arranged separately at a height suitable for operation. This requires a special mechanical transmission between the operating device and the tap changer, which results in an increase in costs.
In another frequently used design, the tap changer is mounted on an intermediate portion protruding from one end wall of the transformer tank. This intermediate portion is provided with side openings to enable the necessary connection of the tap changer to the transformer winding. This alternative structure causes an increase in the dimensions of the transformer.